The field of this invention is that of remotely actuated connectors for connecting pressure vessels together. Most typically, the connection is made between the wellhead housings of oil or gas wells on the ocean floor and a blowout preventer stack. The connection is also frequently used between portions of the blowout preventer stack.
The connectors typically have shoulders on each of the pressure vessels and interconnecting sections or dogs which engage the shoulders. The sections or dogs are driven into engagement by tapered surfaces approaching them. These connectors can be seen in patents such as Haeber U.S. Pat. No. 3,222,088, Ahlstone 3,096,999, Herring U.S. Pat. Nos. 3,492,027, and 3,554,579. These connectors have the characteristic of a tendency to release due to the 4 degree angle of engagement. Literally these connectors frequently have an additional connector means to keep them connected. In some cases they lock the hydraulic fluid in the operating cylinders to keep them locked.
An additional problem with the connectors is that a high make-up preload is desired, but the coefficient of friction can vary between 0.1 and 0.2. The angle of 0.1 coefficient of friction is 5.7 degrees and the angle of 0.2 coefficient of friction is 11.3 degrees. The preload of the connector is a function of the pressure times the sum of the connector angle plus the coefficient of friction angle. This sum is 4xc2x0+5.7xc2x0=9.7xc2x0 in one case and 4xc2x0+11.3xc2x0=15.3xc2x0 in the other case. This is a 15.3xc2x0/9.7xc2x0=57% variation in preload. Contemporary connectors are seeking a 7,000,000 lb. preload, so a 57% change in preload is considerable.
U.S. patent Baugh U.S. Pat. No. 4,516,795 addressed these problems by utilizing a torus ring to actuate the segments, such that the torus ring balanced the forces or even went slightly over center to prevent the tendency to release. A torus is basically a donut shape, with a portion of a torus being any section around the donut. While solving a first problem, the inter-relationship of the torus ring and the conical surfaces of the pressure vessels causes some high contact stress locations which were not desirable. Additionally, when the opposing surfaces of the torus were slipped in relationship to one another, the fit of the parts caused other high contact stress areas.
The Baugh U.S. Pat. No. 4,516,795 connector attempted to control the variation of preload by having a fixed torus diameter, which was not affected by friction angles. A problem associated with this was that the high stress areas would tend to cause wear and require readjustment on the diameter to maintain the predicted preload.
The inter-relationship of the torus profile and the locking of the connector was functionally to xe2x80x9crollxe2x80x9d the locking segment into position over conical clamp hubs. The xe2x80x9crollingxe2x80x9d onto conical clamp hubs inherently caused high stress areas and wear.
The object of this invention is to provide a connector which provides the predictable preload and lack of release tendency associated with the Baugh U.S. Pat. No. 4,516,795 connector, but minimizes the tendency for high stress contact areas associated with the mating torus surfaces between the actuating torus and the locking segments.
A second object of the present invention is to provide a second torus profile for facilitating movement and stress reduction between the locking segment and the locking shoulders on one of the two pressure vessels.
A third object of the present invention is to provide a known orientation between the locking segments during the locking movement such that any wear which occurs will be in the same area and the remaining areas will not be subjected to dimension altering wear movements.
Another object of the present invention is